Project Summary/Abstract Addiction represents a complex genetic psychiatric disorder that likely involves a number of different genes. Addiction to cocaine and other psychostimulants, which are among the most addictive of substances, is also the most heritable. Recently, the ability to reprogram fully differentiated tissues, such as skin, into human induced pluripotent stem cells (hiPSCs) has made it possible to study a multigenic psychiatric disease, such as drug addiction. Cell-based human models for addiction will be created by directly reprogramming skin fibroblasts from methamphetamine-addicted patients and controls into hiPSCs (RFA-DA-11-012). Differentiating these hiPSCs into dopaminergic (DA) neurons will enable the identification of specific genetic and functional changes associated with hiPSC neurons treated with psychostimulants. There are three primary Aims for this R21 proposal. In Aim 1, fibroblasts from 'control' humans will be reprogrammed into hiPSCs and then differentiated into DA neurons. These DA neurons will be transcriptionally profiled in untreated, methamphetamine-treated and methamphetamine-withdrawal conditions to identify the gene pathways affected by methamphetamine treatment and withdrawal. In Aim 2, an electrophysiological characterization of DA neurons differentiated from control hiPSC lines will be completed, followed by studies examining the effect of exposure to methamphetamine treatment and withdrawal. In Aim 3, hiPSCs will be developed from humans addicted to psychostimulants and then examined for differences in properties of these patient-derived neurons and their response to methamphetamine treatment and withdrawal. The hypothesis that hiPSC DA neurons from patients addicted to methamphetamine respond uniquely to methamphetamine treatment in a manner distinct from controls will be tested. Preliminary data are provided that show reprogramming of adult cells into hiPSCs, differentiation of hiPSCs into DA neurons, and basic electrophysiological properties. Studies of patient-derived hiPSC neurons have the potential to significantly advance our understanding of a complex multigenic disorder like drug addiction. The proposed studies have the potential to reveal unique functional differences in DA neurons derived from addicted and control patients, as well as their response to methamphetamine. Results from the proposed studies will likely lead to both the development of improved animal models of addiction and provide an innovative approach for examining the effect of new drug therapies for the treatment of addiction.